The Coronary Artery Surgery Study (CASS) is a multicenter, randomized trial comparing medical and surgical therapy in 780 patients who had mild or moderate angina, or who were asymptomatic after myocardial infarction. The CASS registry population consists of 24,959 patients who had coronary arteriography for suspected ischemic coronary disease at the fifteen participating medical centers. CASS registry patients were enrolled between 1974 and 1979. Eligible registry patients were enrolled in the randomized trial between 1975 and 1979. All registry patients were followed through 1982. Continued follow- up for symptoms and vital status is currently being done by annual contact for the 780 patients in the randomized trial and the 1319 patients who were eligible for randomization but were not enrolled in the trial. Follow-up for vital status for the other registry patients is done through the National Death Index. Contract funds to the CASS Coordinating Center for continued follow-up, data analysis, and preparation of research reports from the registry and randomized trial end in June of 1988. The CASS investigators are proposing to continue follow-up for an additional 5 years and to continue the activity of the CASS investigators in using the extensive CASS data bank for a variety of research protocols.